Some wells produce gas and liquid that is primarily water. The well may have insufficient formation pressure to cause the water to flow to the surface. If not conveyed to the surface, the liquid will build up and block flow of the gas. A variety of techniques are employed to pump the water from the well while allowing the gas to flow. For example, an electrical submersible pump might be installed on a string of tubing to pump the water up the tubing while the gas flows up the annulus.
Electrical submersible pumps, however, do not efficiently pump a mixture of liquid and gas, thus provisions may be required to separate the gas from the liquid. The pump may be housed within a shroud that is suspended in the well on the string of tubing and has an open upper end. The mixed gas and liquid fluid flows up the outer annulus alongside the shroud, then down the inner annulus between the pump and the shroud. As the direction of flow changes, some of the gas is separated from the mixed flow and flows up the outer annulus. The more dense fluid flow down to the intake of the pump, which pumps the more dense fluid up the string of tubing.
U.S. Pat. No. 7,766,081 discloses employing a rotary gas separator to cause additional gas separation of the downward flowing fluid in the inner annulus of the shroud. The rotary gas separator is rotated by the motor. Which is suspended below the shroud. A drive shaft extends through the gas separator to the pump connected to the upper end of the gas separator. The motor rotates vanes within the gas separator to force the liquids to the outer part of the housing of the separator while the gas flows up a central area. A crossover member at the upper end of the separator directs the gas through lateral tubes and out ports in the side wall of the shroud to the outer annulus. The crossover member directs the liquid to the pump, which pumps the liquid up the string of tubing to the surface.
In U.S. Pat. No. 7,766,081, the motor is located entirely below the shroud. The motor relies on the well fluid flowing upward past it for cooling. In some instances, the upward flow may be inadequate. Also, in U.S. Pat. No. 7,766,081, the lateral tubes extending from the cross-over member must be oriented with the gas outlets. Orienting requires that the pump and gas separator be assembled in the shroud before that portion of the shroud is lowered into the well.
Also, in some well production, such as methane from shallow wells, heat must be applied to the well fluid to cause the flow. Provisions to include a heater must account for the shroud, if a shroud for gas separation is employed.